JavaScript: Parse a HTTP Cookie header string and return an object of all cookie name-value pairs

JavaScript fundamental (ES6 Syntax): Exercise-171 with Solution

Parse Cookie Header to Object

Write a JavaScript program to parse a HTTP Cookie header string and return an object of all cookie name-value pairs.

• Use String.prototype.split(';') to separate key-value pairs from each other.
• Use Array.prototype.map() and String.prototype.split('=') to separate keys from values in each pair.
• Use Array.prototype.reduce() and decodeURIComponent() to create an object with all key-value pairs.

Sample Solution:

JavaScript Code:

// Define a function 'parseCookie' that takes a string representing a cookie and parses it into an object
const parseCookie = str =>
  // Split the input string into an array of key-value pairs separated by ';'
  str
    .split(';')
    // Map over the array of key-value pairs and split each pair into an array of key and value
    .map(v => v.split('='))
    // Reduce the array of key-value arrays into an object
    .reduce((acc, v) => {
      // Decode and trim the key and value, then assign them as properties to the accumulator object
      acc[decodeURIComponent(v[0].trim())] = decodeURIComponent(v[1].trim());
      return acc;
    }, {});
// Call the 'parseCookie' function with a sample cookie string and log the result
console.log(parseCookie('foo=bar; equation=E%3Dmc%5E2'));

Output:

{"foo":"bar","equation":"E=mc^2"}

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-171-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that parses an HTTP Cookie header string into an object mapping cookie names to values.
• Write a JavaScript function that splits a cookie string on semicolons and returns a key-value pair object.
• Write a JavaScript program that handles edge cases such as extra spaces and missing values in a cookie header.
• Write a JavaScript function that decodes URL-encoded cookie values while building the object from a cookie header string.

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